Fix setting audio test pipeline volume.

The element setting goes from 0 to 10, with 1 being full volume and anything
above being overdriven. The widget goes from 0-100, so multiplying by 10 is way
outside the limits.

Testing Done:
Changing the volume bar in the preferences window no longer produces a bunch of overflow warnings.

Reviewed at https://reviews.imfreedom.org/r/309/